A linear octasaccharide (molar mass = 1024 g mol-1) on complete hydrolysis produces three monosaccharides: ribose, 2-deoxyribose and glucose. The amount of 2-deoxyribose formed is 58.26 % (w/w) of the total amount of the monosaccharides produced in the hydrolyzed products. The number of ribose unit(s) present in one molecule of octasaccharide is . Use: Molar mass (in g mol-1): ribose = 150, 2-deoxyribose = 134, glucose = 180; Atomic mass (in amu): H = 1, O = 16
Answer
2
Solution
A linear octasaccharide has 7 glycosidic links ⇒ hydrolysis takes up 7 H2O.
Mass of monosaccharides = 1024 + 7 × 18 = 1150 g
2-Deoxyribose = 0.5826 × 1150 = 670 g ⇒ 670134 = 5 units
Remaining 3 units: ribose (r) + glucose (3 - r) with mass 1150 − 670 = 480 g
150r + 180(3 - r) = 480 ⇒ 540 - 30r = 480 ⇒ r = 2
Answer: 2